1. Field of the Invention
The present invention relates to an apparatus for varying an acceptance angle of a light receiver which receives light reflected from an object to be photographed in a camera.
2. Description of the Related Art
In an external light control type of auto strobe which is incorporated in a camera body or detachably attached to a camera body, a light receiving device (light receiver) is provided at a predetermined position of the camera body or the strobe. In such a conventional auto strobe, light emitted from a light emitter and reflected by an object to be photographed is received by the light receiver, so that when the quantity of light received by the light receiver has a predetermined value, the emission of strobe light is stopped to control the quantity of illuminating light (exposure).
However, in the conventional auto strobe, the acceptance angle of the light receiver is constant. Accordingly, in a camera having a focal length varying lens, such as a zoom lens, in which the auto strobe is incorporated, when the focal length is changed, for example from a shortest focal length (WIDE extremity) to an intermediate focal length (standard) or to a longest focal length (TELE extremity) during zooming, the actual photographing range (angle of view) gradually decreases, as shown at 1A, 1B and 1C in FIGS. 7A, 7B and 7C.
However, the light receiving range (acceptance angle) 2 at the respective focal lengths does not vary and is constant.
Therefore, if the light receiving range 2 is set to be optimum at the standard focal length (standard photographing range 1B), the light receiving range 2 at the WIDE extremity is too small to cover the wide photographing range 1A, and conversely, the light receiving range 2 at the TELE extremity is extremely large for the tele photographing range 1C, thus resulting in a reduced precision of light adjustment for a main object in either case.